It's May 1979 in South Wales. Margaret Thatcher is about to win the General Election and six miners are trapped down a coal mine.

And in the compact Playhouse Studio, with a claustrophobic set recreating the darkness of a rubble-strewn mine, it almost feels like you're down there with them. The actors sit on crates in a pit of earth, becoming increasingly sweaty and grimy as time goes on (and shedding their clothes accordingly)

It's the perfect setting for an powerful play packed with secrets, accusations, power tussles, family strife - and politics. Chris Urch doesn't labour the point on the last one, but lets fiery Curly's passionate arguments against a "Nazi with pearls" linger as the men become increasingly desperate. He despairs for a future under Thatcher - and indeed their fate may well be sealed by the actions - or inaction - of those above them in the new world they're yet to enter.

Trapping a group of characters together and seeing what happens next is nothing new, but the execution is almost faultless.

It might be a Welsh mining drama, but the family troubles could be translated to any setting - like Chewy's desperation to leave the family trade behind and start a new life in the big city, miles from brother Curly (a brilliantly intense Tomas Eames)

Laugh-out loud humour cuts through the bleakness of the setting from the very beginning, with naive new boy Mostyn (Joshua Price) revealing his love of Julie Andrews to veteran Bomber (a statesman-like John Cording), earning him her first name as a nickname. Initially he's mocked, but as the reality of the situation sinks in, they join him in a spontaneous rendition of My Favourite Things from The Sound of Music.

Sex and risque humour is another popular subject for the six men. As the group try to advise Mostyn in the art of seduction, Curly announces the youngster needs a party trick - and hilariously reveals his own, giving the name of every element in the periodic table in rapid succession.

It's the smallest moments of humanity that pack the biggest punch, from Mostyn's love for his mum to the excitement over a Blue Riband biscuit in one of their lunch bags.

The banter and singalongs fade as the men's situation worsens, and they are reduced to drinking their own urine, all while playing a guessing game. Later, they have to decide whether to eat a dead body in a bid to survive. It's hard going at times but never less than watchable.

The darkness grows in an over-long and at times over-wrought second act. Tough Cooper breaks down under the pressure and Curly has a long monologue in which he recounts his nightmare about going home, all seeming far removed from the grim realism of the earlier scenes.

The sight of the starving miners scrambling around in the dirt for the crumbs of the last remaining Rich Tea biscuit is heartbreaking and horrifying in equal measure.